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llvm-mirror/test/CodeGen/Thumb2/2009-12-01-LoopIVUsers.ll
Wei Mi 00d0d9c981 [SCEV] Try to reuse existing value during SCEV expansion
Current SCEV expansion will expand SCEV as a sequence of operations
and doesn't utilize the value already existed. This will introduce
redundent computation which may not be cleaned up throughly by
following optimizations.

This patch introduces an ExprValueMap which is a map from SCEV to the
set of equal values with the same SCEV. When a SCEV is expanded, the
set of values is checked and reused whenever possible before generating
a sequence of operations.

The original commit triggered regressions in Polly tests. The regressions
exposed two problems which have been fixed in current version.

1. Polly will generate a new function based on the old one. To generate an
instruction for the new function, it builds SCEV for the old instruction,
applies some tranformation on the SCEV generated, then expands the transformed
SCEV and insert the expanded value into new function. Because SCEV expansion
may reuse value cached in ExprValueMap, the value in old function may be
inserted into new function, which is wrong.
   In SCEVExpander::expand, there is a logic to check the cached value to
be used should dominate the insertion point. However, for the above
case, the check always passes. That is because the insertion point is
in a new function, which is unreachable from the old function. However
for unreachable node, DominatorTreeBase::dominates thinks it will be
dominated by any other node.
   The fix is to simply add a check that the cached value to be used in
expansion should be in the same function as the insertion point instruction.

2. When the SCEV is of scConstant type, expanding it directly is cheaper than
reusing a normal value cached. Although in the cached value set in ExprValueMap,
there is a Constant type value, but it is not easy to find it out -- the cached
Value set is not sorted according to the potential cost. Existing reuse logic
in SCEVExpander::expand simply chooses the first legal element from the cached
value set.
   The fix is that when the SCEV is of scConstant type, don't try the reuse
logic. simply expand it.

Differential Revision: http://reviews.llvm.org/D12090

llvm-svn: 259736
2016-02-04 01:27:38 +00:00

130 lines
6.6 KiB
LLVM

; RUN: opt < %s -O3 | \
; RUN: llc -mtriple=thumbv7-apple-darwin10 -mattr=+neon | FileCheck %s
target datalayout = "e-p:32:32:32-i1:8:32-i8:8:32-i16:16:32-i32:32:32-i64:32:32-f32:32:32-f64:32:32-v64:64:64-v128:128:128-a0:0:32"
define void @fred(i32 %three_by_three, i8* %in, double %dt1, i32 %x_size, i32 %y_size, i8* %bp) nounwind {
entry:
; -- The loop following the load should only use a single add-literation
; instruction.
; CHECK: vldr
; CHECK-NOT: adds
; CHECK: subsections_via_symbols
%three_by_three_addr = alloca i32 ; <i32*> [#uses=2]
%in_addr = alloca i8* ; <i8**> [#uses=2]
%dt_addr = alloca float ; <float*> [#uses=4]
%x_size_addr = alloca i32 ; <i32*> [#uses=2]
%y_size_addr = alloca i32 ; <i32*> [#uses=1]
%bp_addr = alloca i8* ; <i8**> [#uses=1]
%tmp_image = alloca i8* ; <i8**> [#uses=0]
%out = alloca i8* ; <i8**> [#uses=1]
%cp = alloca i8* ; <i8**> [#uses=0]
%dpt = alloca i8* ; <i8**> [#uses=4]
%dp = alloca i8* ; <i8**> [#uses=2]
%ip = alloca i8* ; <i8**> [#uses=0]
%centre = alloca i32 ; <i32*> [#uses=0]
%tmp = alloca i32 ; <i32*> [#uses=0]
%brightness = alloca i32 ; <i32*> [#uses=0]
%area = alloca i32 ; <i32*> [#uses=0]
%y = alloca i32 ; <i32*> [#uses=0]
%x = alloca i32 ; <i32*> [#uses=2]
%j = alloca i32 ; <i32*> [#uses=6]
%i = alloca i32 ; <i32*> [#uses=1]
%mask_size = alloca i32 ; <i32*> [#uses=5]
%increment = alloca i32 ; <i32*> [#uses=1]
%n_max = alloca i32 ; <i32*> [#uses=4]
%temp = alloca float ; <float*> [#uses=1]
%"alloca point" = bitcast i32 0 to i32 ; <i32> [#uses=0]
store i32 %three_by_three, i32* %three_by_three_addr
store i8* %in, i8** %in_addr
%dt = fptrunc double %dt1 to float ; <float> [#uses=1]
store float %dt, float* %dt_addr
store i32 %x_size, i32* %x_size_addr
store i32 %y_size, i32* %y_size_addr
store i8* %bp, i8** %bp_addr
%0 = load i8*, i8** %in_addr, align 4 ; <i8*> [#uses=1]
store i8* %0, i8** %out, align 4
%1 = call i32 (...) @foo() nounwind ; <i32> [#uses=1]
store i32 %1, i32* %i, align 4
%2 = load i32, i32* %three_by_three_addr, align 4 ; <i32> [#uses=1]
%3 = icmp eq i32 %2, 0 ; <i1> [#uses=1]
br i1 %3, label %bb, label %bb2
bb: ; preds = %entry
%4 = load float, float* %dt_addr, align 4 ; <float> [#uses=1]
%5 = fpext float %4 to double ; <double> [#uses=1]
%6 = fmul double %5, 1.500000e+00 ; <double> [#uses=1]
%7 = fptosi double %6 to i32 ; <i32> [#uses=1]
%8 = add nsw i32 %7, 1 ; <i32> [#uses=1]
store i32 %8, i32* %mask_size, align 4
br label %bb3
bb2: ; preds = %entry
store i32 1, i32* %mask_size, align 4
br label %bb3
bb3: ; preds = %bb2, %bb
%9 = load i32, i32* %mask_size, align 4 ; <i32> [#uses=1]
%10 = mul i32 %9, 2 ; <i32> [#uses=1]
%11 = add nsw i32 %10, 1 ; <i32> [#uses=1]
store i32 %11, i32* %n_max, align 4
%12 = load i32, i32* %x_size_addr, align 4 ; <i32> [#uses=1]
%13 = load i32, i32* %n_max, align 4 ; <i32> [#uses=1]
%14 = sub i32 %12, %13 ; <i32> [#uses=1]
store i32 %14, i32* %increment, align 4
%15 = load i32, i32* %n_max, align 4 ; <i32> [#uses=1]
%16 = load i32, i32* %n_max, align 4 ; <i32> [#uses=1]
%17 = mul i32 %15, %16 ; <i32> [#uses=1]
%18 = call noalias i8* @malloc(i32 %17) nounwind ; <i8*> [#uses=1]
store i8* %18, i8** %dp, align 4
%19 = load i8*, i8** %dp, align 4 ; <i8*> [#uses=1]
store i8* %19, i8** %dpt, align 4
%20 = load float, float* %dt_addr, align 4 ; <float> [#uses=1]
%21 = load float, float* %dt_addr, align 4 ; <float> [#uses=1]
%22 = fmul float %20, %21 ; <float> [#uses=1]
%23 = fsub float -0.000000e+00, %22 ; <float> [#uses=1]
store float %23, float* %temp, align 4
%24 = load i32, i32* %mask_size, align 4 ; <i32> [#uses=1]
%25 = sub i32 0, %24 ; <i32> [#uses=1]
store i32 %25, i32* %j, align 4
br label %bb5
bb4: ; preds = %bb5
%26 = load i32, i32* %j, align 4 ; <i32> [#uses=1]
%27 = load i32, i32* %j, align 4 ; <i32> [#uses=1]
%28 = mul i32 %26, %27 ; <i32> [#uses=1]
%29 = sitofp i32 %28 to double ; <double> [#uses=1]
%30 = fmul double %29, 1.234000e+00 ; <double> [#uses=1]
%31 = fptosi double %30 to i32 ; <i32> [#uses=1]
store i32 %31, i32* %x, align 4
%32 = load i32, i32* %x, align 4 ; <i32> [#uses=1]
%33 = trunc i32 %32 to i8 ; <i8> [#uses=1]
%34 = load i8*, i8** %dpt, align 4 ; <i8*> [#uses=1]
store i8 %33, i8* %34, align 1
%35 = load i8*, i8** %dpt, align 4 ; <i8*> [#uses=1]
%36 = getelementptr inbounds i8, i8* %35, i64 1 ; <i8*> [#uses=1]
store i8* %36, i8** %dpt, align 4
%37 = load i32, i32* %j, align 4 ; <i32> [#uses=1]
%38 = add nsw i32 %37, 1 ; <i32> [#uses=1]
store i32 %38, i32* %j, align 4
br label %bb5
bb5: ; preds = %bb4, %bb3
%39 = load i32, i32* %j, align 4 ; <i32> [#uses=1]
%40 = load i32, i32* %mask_size, align 4 ; <i32> [#uses=1]
%41 = icmp sle i32 %39, %40 ; <i1> [#uses=1]
br i1 %41, label %bb4, label %bb6
bb6: ; preds = %bb5
br label %return
return: ; preds = %bb6
ret void
}
declare i32 @foo(...)
declare noalias i8* @malloc(i32) nounwind